So here’s a guide to help you avoid it. To side-step catching it in the first place, and protect yourself when other people around you come down with it.

You can be unlucky, of course. But nine times out of ten, these simple tips should help you stay out of trouble.

First off, know that norovirus is very, very virulent – an unpleasant illness on a hair trigger that is easily touched off. Other viruses and most bacteria need at least 20 or 30 cells to attack you with if they’re going to infect you.

Norovirus only needs half that, which makes it twice as dodgy. A nasty, horrible illness that’s super-contagious – spread mostly by touch, but also in the air. Get it on your fingers, your clothing or your skin and you have to be really careful.

It’s also pernicious, at home anywhere and able to survive on most surfaces for over a month. And since it spreads so easily, anything touched by other people is a possible contact point – especially high-touch objects like door handles, grab rails, light switches, phones, keypads and cutlery you eat with.

How does it get into your body?

Usually through your mouth. You can breathe it in or swallow it, either on contaminated food or anything eaten with your fingers.

But note the common denominator – all finger food. Stuff you can scoff with your hands, right in the middle of doing something else. Or anything with a lot of handling by others around you – tear-and-share, buffets, smorgasbords, group curries.

All easily contaminated by just one person’s unclean fingers –including yours.

Finger-lickin’ good, maybe – fingers pointing at trouble more like.

Big tummy trouble.

Self-inflicted misery

And that’s the bummer.

Because most of the time we eat without thinking because our hands LOOK clean. Yet realistically our fingers could be loaded with all kinds of yuk too small to see – a single norovirus cell is just 2 microns across, about a 10,000th the width of a human hair.

It floats around easily in the air, lighter than cigarette smoke. And settles invisibly on your skin, scraping together easily with its brothers and sisters as you wipe your hand across – groups of 20, 500, 1,000 cells, all ready to go.

Which brings us to Reality Check One – most norovirus attacks are self-inflicted. The stuff is already on our skin and we don’t even know it. We let our hygiene lapse at the wrong moment – and four hours later it’s cramps, vomiting and diarrhoea like we don’t ever want to believe.

Because when does anyone get the chance, on the go most of the time – especially on holiday?

But unfortunately, that’s not good enough if you want to skip the spoil-sport tummy-torture. All it needs is ONE slip up, one forgetful moment with unwashed paws, and you’ll be chundering through the next few days.

One in the eye

Uh huh. So here’s a memory jogger.

You’re on the beach, yeah? Slapping on the suntan lotion. You wipe your hands down, but somehow, you touch your face – and the stuff gets in your eye.

Yeow, itch, instant anguish. Your whole day scuppered till you get back to the hotel, rinse your eye out and sit there with a damp cloth to your face for an hour. But let that tell you something.

That’s how norovirus works.

It’s a fact of life that we touch our faces all the time – 2,000-3,000 times a day for some of us. And that’s norovirus’s easiest way into our bodies – through the soft tissue of our eyes and mouth.

Suntan lotion on your fingers just loses you a day. Norovirus on your fingers can screw your whole holiday – or your wedding, or your graduation, or anything else it’s the pits to lose out on.

Shocking revelation isn’t it, to sit down to this slap-up dinner after a wonderful day – and suddenly realise that with all the places you’ve been and things you’ve done, you haven’t washed your hands since breakfast?

So Reality Check Two – handling norovirus means hiking our personal hygiene to a whole different level. Day-to-day, what we’re living with most of the time is “low-giene”.

Yeah, yeah, dirty hands. But you see these reports all the time, lots of people all getting sick at the same – what about food poisoning? Don’t vendors and restaurants serve food that’s contaminated?

For sure. And we all know the cause. Either the food itself is off, or is touched in preparation by someone with dirty hands.

Not as common as you might think, because anywhere that sells food wants to be in business today AND tomorrow. They also have laws to follow, standards to observe, codes of practice. So most of the time, they DO take care. A law suit could cost big money – and easily be the end of them.

So how can you tell if it’s self-inflicted or food poisoning?

Your fault or theirs?

Reality Check Three – the vomiting, the diarrhoea, they’re earth-shatteringly violent because that’s how norovirus spreads itself – as far and wide as possible, very quickly.

Even so, it takes time to assert itself – and from that, you can often tell how it started.

If an outbreak happens in ones and twos, it’s probably triggered by an individual – either from unwashed hands or by suspect food from an external source – something eaten before they arrived where you are. Unwashed hands most likely – suspect self-inflicted

If a whole crowd of people comes down together, that suggests they were exposed simultaneously – some kind of shared experience. That could be either from something they’ve eaten – they were all served the same dish at the same time. Unwashed hands most likely again – though this time in preparing a popular food dish – suspect staff hygiene lapse, or dodgy food source.

Norovirus also triggers by mishap, as happened in a Swiss hotel – bad luck for everyone in the place, who all came down with it at once. Flash flooding from a cloudburst overwhelmed the drains, forcing guests and staff to wade through water backed up from the toilets.

An outbreak was inevitable, however much everyone washed themselves and their clothes – furniture, fittings and all facilities were all heavily contaminated – instant infection until they were destroyed and the whole building sanitised.

Bad, bad boomerang

Which leads to Realty Check Four – the norovirus boomerang effect. The virus returns very easily to cause repeat outbreaks if it is not completely and utterly removed after the hit in the first place.

Cruise liners are really prone to this for two reasons. Lots of people close together in shared eating and living space, handling the same objects. Plus millions of nooks and crannies where the virus can hide during even the most rigorous scrub-downs.

The handling thing is a nightmare, as there are endless things that everybody touches that can pass on by contact. Called fomites, these germ-transfer items include glasses, knives and forks, deck chairs, gym equipment, poker chips, playing cards, courtesy bibles, whatever – all of which have to be individually sanitised to avoid repeats.

Repeat outbreaks happened recently with Fred Olsen Line’s Balmoral – struck down 6 times since 2009 – and a latest misfortune just last month that ruined an Old England to New England cruise for hundreds of passengers.

Holland America Line’s Caribbean cruise liner Amsterdam was also unlucky – having to cancel four trips in succession because of repeat outbreaks in 1982. It got so bad, the ship had to be taken out of service to ensure thorough decontamination – and new passengers were even warned before embarking that the ship had previously had problems it couldn’t get rid of.

Get out of jail, free

Doom and gloom? Avoid holidays like the plague?

You can just as easily catch norovirus at home, just by forgetting to wash your hands.

And that’s the key to a perfect holiday, even the stay-at-home kind. Always wash your hands before putting anything in your mouth. And keep your hands clean too. Your fingers might be safe, but the things you touch with them are almost certainly not – indoors or outdoors, germs are a reality we have to live with.

Recognising that, plan for when you can’t wash your hands too.

Always carry hand-wipes, even if they’re not antibacterial. Easy enough to use, right at the dinner table – and doing it properly will get rid norovirus and 99.9% of all other germs.

Handbag size antibacterial gel is good too – the alcohol base kills germs, though is not as effective as physically wiping them away.

Beyond that, be careful.

If somebody close to you comes down with norovirus, you don’t need to get it too. Obviously avoid accident areas of vomit or diarrhoea. Keep well clear, the yuk can spread several feet in all directions.

Be aware though that normal disinfecting is unlikely to go far enough. The whole place needs a good going-over, especially every last nook and cranny if the virus is not to come back again.

Almost impossible with scrubbing and bleach, the easy way is with ionised hydrogen peroxide – misted up into the air by a Hypersteriliser and electrostatically charged so it disperses actively in all directions, killing airborne and surface germs deep into every crack and crevice.

Seems every few weeks there’s another cruise ship in to be deep-cleaned and fumigated – another hospital ward closed and out of action.

This time it’s Fred Olsen’s flagshipBalmoral again, back less than a month after the last norovirus hit. A setback this fine Norwegian cruise line does not deserve – especially when it looks like a passenger brought it on board with them.

No cure, no warning

But that’s the thing with norovirus – the complete lack of warning. Today you’re right as rain, 48 hours later you’re as sick as a dog.

That poor passenger walked up the gangplank, all fine and dandy – to be struck down with cramps and endless hours on the hopper. And endless more, driving the bus.

Not fair.

Er, almost. At least it’s not the cruise line’s fault.

But that’s the other thing about norovirus. Most of the time we bring it on ourselves.

Oh yes, we do.

Because without a doubt, the biggest cause of norovirus is not washing our hands – which almost all of us forget to do when we’re having fun. Or avoid.

Not a wise mistake to make. Norovirus is easily spread and highly contagious. The Don’t-Wash-Hands Disease.

All those things you touch

You pick it up slamming a taxi door – next moment you’re wolfing a chicken and bacon baguette between meetings and – boom! You didn’t wash your hands, did you? You swallowed the germs. Two days time and you’re hurling your guts out.

Unless you wash your hands – get rid of the germs that surround you every day whenever you can. Otherwise, you get on a cruise ship and it goes round like wildfire.

Well of course it does – there’s thousands of you all living close next-door to each other, sharing the same bathrooms, eating in the same space. It’s a wonder they ever stop it at all.

Unlucky for some

And just occasionally they don’t – like on this latest cruise with the Balmoral.

They could have been unlucky though, as happened to Holland America Line’s Amsterdam, back in 2002. The stuff lingers, you see – can survive on all kinds of surfaces for weeks. And cruise ships are usually turned round in just days – they can’t afford myths.

Four times, one after the other, Amsterdam set out on a new cruise – and four times, one after the other, norovirus made her turn back, hardly into the voyage. There are so many nooks and crevices on a cruise liner, even deep cleaning may not get all of the bug out – they even had to scrub individual poker chips in the casino!

A more effective way

Easier to use Hypersterilisers – a whole batch of them ganged together can do the ship overnight.

They work on ionised hydrogen peroxide, see. Negatively-charged microscopic molecules all repelling each other, forcing themselves into the tightest, smallest, most out-of-the-way places, trying to escape each other.

Riding up into the air too – and hard up against every surface. Underneath and behind too. Actively dispersing like no ordinary disinfectant spray ever can – a supercharged gas plasma grabbing at positively charged viruses and bacteria it meets on the way and oxidising them to destruction.

All viruses, all bacteria – norovirus too. And Ebola, if you’re cruising West Africa.

And safe too – reverting back to just oxygen and water when it’s done. No need for masks like they had to wear on Balmoral – though it can catch your throat when it’s working, so best to stay away for the odd hour.

No smell either – no chemical after-pong or nothing.

A good thing too. Smell is a good give-away that germs are still working – the easy way to tell that food is off. It’s why the loo pongs too – if it’s not clean.